Last week, we reported on a slew of new titles arriving on the Xbox 360’s “Games on Demand” service; however, two additional titles appear to have stealthily made their way onto the console with little fanfare [via Joystiq].

Capcom’s Super Street Fighter IV has been added to the Marketplace for a price of $40 (in the US, specifically). Also available this month is the tactical role-playing title Operation Darkness for $40 (US). While the box art for the RPG includes the word “Success,” potential buyers should note it only refers to the name of the game’s developer and not its critical reception.

Pricing and game availability may differ based on region. Operation Darkness’ tepid critical reception is available worldwide.